A=[1 2 -13; 3 -2 1];
A(2,:)=A(2,:)-3*A(1,:);
A(2,:)=-A(2,:)/8;
A(1,:)=A(1,:)-2*A(2,:);
A

% x1+2x2=-13  -> x2=(-x1-13)/2
% 3x1-2x2=1 -> x2=(3x1-1)/2
x1=-5:0.01:0;
plot(x1,(-x1-13)/2,x1,(3*x1-1)/2);
axis square
grid on
xlabel('x_1');
ylabel('x_2')
legend('Line 1: x_1+2x_2=-13', 'Line 2: 3x_1-2x_2=1')